1. Field of the Invention
This invention relates to locking apparatus suitable for use with a manually operated control and more specifically, but not exclusively, with a handle operated control such as a valve.
One type of commonly-used control is a fluid flow valve which includes a rotatable lever handle which may be rotated between an open position to allow the flow of fluid through the valve and a closed position to shut off the flow of fluid.
One problem which may be encountered with the above type of valve arises because it is possible to move the handle from either position with relative ease. Thus there is always the potential that a handle may be set to the wrong position by accident, for example, by knocking the handle. The handle may also be set to the wrong position by a person acting maliciously.
It may, for example, be necessary to use the valve to shut off the flow of toxic fluid carried along a pipe line while maintenance work is performed. If, whilst this work was being performed, the valve were accidentally turned on thereby allowing the flow of toxic fluid to resume it could prove dangerous and possibly fatal to whoever was performing the maintenance work.
There may also be situations in which it is important that a valve be kept open for a certain amount of time, and in which it is highly undesirable that the valve be closed.
There are, indeed, many situations in which it is undesirable, if not essential, that valves are not accidentally or intentionally moved from the required position. It would therefore be useful to be able to prevent the valve handle being moved out of position.
2. Summary of the Prior Art
U.S. Pat. No. 5,003,797 discloses a locking device for a valve having a lever handle. The device includes a channel member defining a channel to receive a section of the lever handle when closed and a leg that bears against the valve or pipeline connected to it. A lock is inserted through the apertures in the channel member alongside an edge of the handle. However, this device is necessarily relatively large and may be cumbersome. Also, the above device can only be fitted on a valve the handle of which is in one specific position e.g. a closed position.